ABSTRACT
This chapter gives an overview of the crystallographic aspects of Thallium-based superconductors. It concerns the general structure of Thallium-based compounds. Nonstoichiometry and cation substitution are discussed in relation to hole carrier creation and structural stability. A Crystal structures in this series are refined using single-crystal x-ray, powder neutron, and powder x-ray diffraction data. Structural defects caused by substitution have been investigated by high-resolution electron microscopy to compare the experimental through-focus series with the images calculated for various crystal thicknesses. The systematic structural changes that accompany changes in oxygen content have been clarified using powder x-ray and neutron diffraction data. These structural changes are explained by the release of oxygen atoms, which decreases the amount of hole carriers in the Copper(II) oxide layer.
